Silicone containing materials are widely applied to film, paper and other substrates to impart release properties thereto. Historically, many of these silicone materials have been solvent based and catalyzed by metallic catalysts such as tin, rhodium or platinum. These release coatings have provided desirable levels of release for many applications. However, because of increased environmental concerns regarding the release of volatile organic compounds (VOCs) that can result from the use of such solvent based systems, the industry has been shifting its focus to solventless (100% solids) release systems.
Solventless systems include thermally cured silicone release compositions (e.g. platinum catalyzed systems) and radiation cured systems (cured by UV or EB radiation). Thermally cured silicone release systems can require large quantities of energy and extensive manufacturing floor space for the thermal cure equipment. Radiation cured systems require less manufacturing floor space and are more energy efficient. However, many release liner manufacturers have invested heavily in thermal cure equipment that is not readily displaced and/or converted to radiation curing lines.
Both solvent based and solventless silicone release systems can impart desirable release properties to the substrate to which it is applied. However, an increasing number of applications require a silicone release coating that minimizes the migration or transfer of unreacted silicone compounds in the release coating onto an adjacent surface such as an adhesive or the backside of the support substrate in addition to providing the desired release level.
For example, unreacted or non-crosslinked silicone compounds present in the cured silicone release layer can migrate onto an adjacent adhesive layer and reduce its adhesive properties. Silicone migration or volatilization is also problematic for silicone-sensitive end uses, such as in the microelectronics and automotive industries. Silicones can also transfer to the backside of the support substrate of a release liner stored in roll form resulting in a surface that is difficult or impossible to print. Furthermore, the silicone which transfers to the backside of the support substrate can re-transfer to another substrate which has been adhesively or otherwise laminated to the release liner. This re-transfer of silicone can also cause printing problems such as poor adhesion or non-wetting of the ink.